path: root/testtools/matchers/_higherorder.py

# Copyright (c) 2009-2012 testtools developers. See LICENSE for details.

__all__ = [
    'AfterPreprocessing',
    'AllMatch',
    'Annotate',
    'AnyMatch',
    'MatchesAny',
    'MatchesAll',
    'Not',
    ]

import types

from ._impl import (
    Matcher,
    Mismatch,
    MismatchDecorator,
    )


class MatchesAny:
    """Matches if any of the matchers it is created with match."""

    def __init__(self, *matchers):
        self.matchers = matchers

    def match(self, matchee):
        results = []
        for matcher in self.matchers:
            mismatch = matcher.match(matchee)
            if mismatch is None:
                return None
            results.append(mismatch)
        return MismatchesAll(results)

    def __str__(self):
        return "MatchesAny(%s)" % ', '.join([
            str(matcher) for matcher in self.matchers])


class MatchesAll:
    """Matches if all of the matchers it is created with match."""

    def __init__(self, *matchers, **options):
        """Construct a MatchesAll matcher.

        Just list the component matchers as arguments in the ``*args``
        style. If you want only the first mismatch to be reported, past in
        first_only=True as a keyword argument. By default, all mismatches are
        reported.
        """
        self.matchers = matchers
        self.first_only = options.get('first_only', False)

    def __str__(self):
        return 'MatchesAll(%s)' % ', '.join(map(str, self.matchers))

    def match(self, matchee):
        results = []
        for matcher in self.matchers:
            mismatch = matcher.match(matchee)
            if mismatch is not None:
                if self.first_only:
                    return mismatch
                results.append(mismatch)
        if results:
            return MismatchesAll(results)
        else:
            return None


class MismatchesAll(Mismatch):
    """A mismatch with many child mismatches."""

    def __init__(self, mismatches, wrap=True):
        self.mismatches = mismatches
        self._wrap = wrap

    def describe(self):
        descriptions = []
        if self._wrap:
            descriptions = ["Differences: ["]
        for mismatch in self.mismatches:
            descriptions.append(mismatch.describe())
        if self._wrap:
            descriptions.append("]")
        return '\n'.join(descriptions)


class Not:
    """Inverts a matcher."""

    def __init__(self, matcher):
        self.matcher = matcher

    def __str__(self):
        return 'Not({})'.format(self.matcher)

    def match(self, other):
        mismatch = self.matcher.match(other)
        if mismatch is None:
            return MatchedUnexpectedly(self.matcher, other)
        else:
            return None


class MatchedUnexpectedly(Mismatch):
    """A thing matched when it wasn't supposed to."""

    def __init__(self, matcher, other):
        self.matcher = matcher
        self.other = other

    def describe(self):
        return "{!r} matches {}".format(self.other, self.matcher)


class Annotate:
    """Annotates a matcher with a descriptive string.

    Mismatches are then described as '<mismatch>: <annotation>'.
    """

    def __init__(self, annotation, matcher):
        self.annotation = annotation
        self.matcher = matcher

    @classmethod
    def if_message(cls, annotation, matcher):
        """Annotate ``matcher`` only if ``annotation`` is non-empty."""
        if not annotation:
            return matcher
        return cls(annotation, matcher)

    def __str__(self):
        return 'Annotate({!r}, {})'.format(self.annotation, self.matcher)

    def match(self, other):
        mismatch = self.matcher.match(other)
        if mismatch is not None:
            return AnnotatedMismatch(self.annotation, mismatch)


class PostfixedMismatch(MismatchDecorator):
    """A mismatch annotated with a descriptive string."""

    def __init__(self, annotation, mismatch):
        super().__init__(mismatch)
        self.annotation = annotation
        self.mismatch = mismatch

    def describe(self):
        return '{}: {}'.format(self.original.describe(), self.annotation)


AnnotatedMismatch = PostfixedMismatch


class PrefixedMismatch(MismatchDecorator):

    def __init__(self, prefix, mismatch):
        super().__init__(mismatch)
        self.prefix = prefix

    def describe(self):
        return '{}: {}'.format(self.prefix, self.original.describe())


class AfterPreprocessing:
    """Matches if the value matches after passing through a function.

    This can be used to aid in creating trivial matchers as functions, for
    example::

      def PathHasFileContent(content):
          def _read(path):
              return open(path).read()
          return AfterPreprocessing(_read, Equals(content))
    """

    def __init__(self, preprocessor, matcher, annotate=True):
        """Create an AfterPreprocessing matcher.

        :param preprocessor: A function called with the matchee before
            matching.
        :param matcher: What to match the preprocessed matchee against.
        :param annotate: Whether or not to annotate the matcher with
            something explaining how we transformed the matchee. Defaults
            to True.
        """
        self.preprocessor = preprocessor
        self.matcher = matcher
        self.annotate = annotate

    def _str_preprocessor(self):
        if isinstance(self.preprocessor, types.FunctionType):
            return '<function %s>' % self.preprocessor.__name__
        return str(self.preprocessor)

    def __str__(self):
        return "AfterPreprocessing({}, {})".format(
            self._str_preprocessor(), self.matcher)

    def match(self, value):
        after = self.preprocessor(value)
        if self.annotate:
            matcher = Annotate(
                "after {} on {!r}".format(self._str_preprocessor(), value),
                self.matcher)
        else:
            matcher = self.matcher
        return matcher.match(after)


# This is the old, deprecated. spelling of the name, kept for backwards
# compatibility.
AfterPreproccessing = AfterPreprocessing


class AllMatch:
    """Matches if all provided values match the given matcher."""

    def __init__(self, matcher):
        self.matcher = matcher

    def __str__(self):
        return 'AllMatch({})'.format(self.matcher)

    def match(self, values):
        mismatches = []
        for value in values:
            mismatch = self.matcher.match(value)
            if mismatch:
                mismatches.append(mismatch)
        if mismatches:
            return MismatchesAll(mismatches)


class AnyMatch:
    """Matches if any of the provided values match the given matcher."""

    def __init__(self, matcher):
        self.matcher = matcher

    def __str__(self):
        return 'AnyMatch({})'.format(self.matcher)

    def match(self, values):
        mismatches = []
        for value in values:
            mismatch = self.matcher.match(value)
            if mismatch:
                mismatches.append(mismatch)
            else:
                return None
        return MismatchesAll(mismatches)


class MatchesPredicate(Matcher):
    """Match if a given function returns True.

    It is reasonably common to want to make a very simple matcher based on a
    function that you already have that returns True or False given a single
    argument (i.e. a predicate function).  This matcher makes it very easy to
    do so. e.g.::

      IsEven = MatchesPredicate(lambda x: x % 2 == 0, '%s is not even')
      self.assertThat(4, IsEven)
    """

    def __init__(self, predicate, message):
        """Create a ``MatchesPredicate`` matcher.

        :param predicate: A function that takes a single argument and returns
            a value that will be interpreted as a boolean.
        :param message: A message to describe a mismatch.  It will be formatted
            with '%' and be given whatever was passed to ``match()``. Thus, it
            needs to contain exactly one thing like '%s', '%d' or '%f'.
        """
        self.predicate = predicate
        self.message = message

    def __str__(self):
        return '{}({!r}, {!r})'.format(
            self.__class__.__name__, self.predicate, self.message)

    def match(self, x):
        if not self.predicate(x):
            return Mismatch(self.message % x)


def MatchesPredicateWithParams(predicate, message, name=None):
    """Match if a given parameterised function returns True.

    It is reasonably common to want to make a very simple matcher based on a
    function that you already have that returns True or False given some
    arguments. This matcher makes it very easy to do so. e.g.::

      HasLength = MatchesPredicate(
          lambda x, y: len(x) == y, 'len({0}) is not {1}')
      # This assertion will fail, as 'len([1, 2]) == 3' is False.
      self.assertThat([1, 2], HasLength(3))

    Note that unlike MatchesPredicate MatchesPredicateWithParams returns a
    factory which you then customise to use by constructing an actual matcher
    from it.

    The predicate function should take the object to match as its first
    parameter. Any additional parameters supplied when constructing a matcher
    are supplied to the predicate as additional parameters when checking for a
    match.

    :param predicate: The predicate function.
    :param message: A format string for describing mis-matches.
    :param name: Optional replacement name for the matcher.
    """
    def construct_matcher(*args, **kwargs):
        return _MatchesPredicateWithParams(
            predicate, message, name, *args, **kwargs)
    return construct_matcher


class _MatchesPredicateWithParams(Matcher):

    def __init__(self, predicate, message, name, *args, **kwargs):
        """Create a ``MatchesPredicateWithParams`` matcher.

        :param predicate: A function that takes an object to match and
            additional params as given in ``*args`` and ``**kwargs``. The
            result of the function will be interpreted as a boolean to
            determine a match.
        :param message: A message to describe a mismatch.  It will be formatted
            with .format() and be given a tuple containing whatever was passed
            to ``match()`` + ``*args`` in ``*args``, and whatever was passed to
            ``**kwargs`` as its ``**kwargs``.

            For instance, to format a single parameter::

                "{0} is not a {1}"

            To format a keyword arg::

                "{0} is not a {type_to_check}"
        :param name: What name to use for the matcher class. Pass None to use
            the default.
        """
        self.predicate = predicate
        self.message = message
        self.name = name
        self.args = args
        self.kwargs = kwargs

    def __str__(self):
        args = [str(arg) for arg in self.args]
        kwargs = ["%s=%s" % item for item in self.kwargs.items()]
        args = ", ".join(args + kwargs)
        if self.name is None:
            name = 'MatchesPredicateWithParams({!r}, {!r})'.format(
                self.predicate, self.message)
        else:
            name = self.name
        return '{}({})'.format(name, args)

    def match(self, x):
        if not self.predicate(x, *self.args, **self.kwargs):
            return Mismatch(
                self.message.format(*((x,) + self.args), **self.kwargs))